First thing I look for is the size, as lots of bridles dont come in extra full! which I count as comfort!
Then Leather Quality then appearance, have to say dont really go for brands, after seeing a hideos bridle from a well known brand a livery bought more money than sense!
Depends what you are buying the bridle for. I've found it cheaper to buy a 'foreign' bridle instead of new rubber reins as you can get a whole bridle for a tenner, but you can pay £30 for reins. In which case it wouldn't matter what it looked like as I wouldn't wear it anywhere but at home.
However if I was buying one for shows I would want it to look pretty!